E] DIEN THPdNG THifC
He thong dien hq dp
HoIng Hiiru Thin
C
hu trflong didn khf h o i t o i n qudc d i dfla di^n ddn h l u khIp cic gia dinh, t f l t h i n h thj ddn ndng thdn, tfl midn xudi Idn midn ngflpe, tfl midn bidn ddn vflng nfli hdo l i n h . Didn dem lai i n h sing, ngudn ddng Ipe, tao ra cfldc sdng d i y tidn nghi. Bdn c?nh dd, di^n eung g i y nhflng he luy cho ngfldi dflng, nhflng hdng hdc, b i t thfldng khd khIe phuc. Tai n?n vd didn ludn rinh r i p tfl trd em ddn cu g i i .He thdng didn (HTD) bao gdm ba p h i n tfl cd b i n I I a) ngudn didn (cac n h i m i y didn) - p h i n tfl sin x u l t ra didn;
b) tfldi didn - p h i n tfl thu gom v i truydn t i i didn ddn noi tieu thu va e) hd dung didn - ndi didn dflpc sfl dung nhfl mdt hang h o i nang Iflpng phuc vy s i n xult v i ddi sdng.
Do nhu c l u truyen t i i v l p h i n phdi, lfldi didn chia ra a) ludi sieu cao ap (tfl 330 kV trd Idn, nude ta sfldung d p 500 kV); b) lUdi cao i p (tfl 66 kV den dfldi 300 kV, nfldc ta sfldung d p 220 kV va 110 kV); c) lUdl t r u n g ap (tfl trdn 1 kV ddn dfldi 60 kV, d nfldc ta qui djnh mdt d p - d p chuan 22 kV v i e l p cho phep 35 kV) v i d) lUdi ha ap (dfldi 1 kV, d nflde ta dung d p 0,4 kV).
Lfldi ha i p (HA) e l p dien dung trong sinh hoat va tieu dung, thfldng gpi l i Ifldi sinh hoat, dflpe t r i i d i i khIp noi cd hd dung didn, phuc vu chidu sing, thdng gid (quat), dieu hoa, thiet bj lanh, thidt bj e l p nhiet, bdm nfldc, ngudn d p cac thidt b| didn t f l v i nhidu thfl khic ndn l i Ifldi hdt sflc g i n gui vdi ngfldi dung dien. Thudng thflc dung dien ehu ydu de cap den lfldi HA. Theo thdi quen, Ifldi HA cdn gpi l i Ifldi ha thd. Hai t h u i t ngfl n i y l i tUPng ddng.
Ludi HA ludn l i ludi ba pha trung tfnh true tiep ndi d i t (hinh 1.1). Diy q u i n ngudn (day q u i n cung d p didn i p v i cdng suit eho ludi) loai ba pha a, b, c d I u sao cd diem trung tfnh n 6\sac ndi trflc tidp xudng d i t . D i u ra cfla d i y q u i n ngudn ba pha l i ba day pha, edn gpi la day lijra (a, b, e) v i d i y trung tinh, edn gpi la ddy ngudi (n). Do day ngudi ndi d i t , khdng cd hieu the vdi d i t ndn khi ngfldi dflng trdn d i t tidp xuc vdi nd, khdng cd hidu thd d i t v i o ngfldi - d i t , ngfldi khdng bi"didn g i i t " vl thd gpi l i d i y ngfldi.
Hieu the gifla mdi d i y pha (a, b, c) vdi day n (cung l i dit) gpi la didn I p pha • ddt, cdn gpi l i didn i p pha.
Trong hd HA - 0,4 kV, didn i p pha danh djnh l i 220 V.
Hidu thd gifla hai d i y pha (a-b, b-c va c-a) gpi I I didn I p pha - pha, edn gpi l i didn dp ddy. Trong he HA - 0,4 kV, didn I p d i y danh djnh la 380 V. Vi the, he HA - 0,4 kV edn gpi la he 380/220 V
Do mdi d i y pha cd didn I p pha - d i t , ndn ngfldi dflng trdn m^t d i t tidp xflc vdi d i y pha sd ehju didn I p niy.
Ndu ngfldi cd dl g i n g , ung cich didn hoic dflng klm cich didn tidp xfle, se khdng cd ddng didn qua ngfldi v i do dd, khdng bj didn gi|t. TrUdng hpp vd tinh ch?m v i o d i y pha, do g i l y ddp bj I m , sd cd ddng didn qua ngUdi v i do dd se bj didn giit.
day quan nguon
Hinh 1.1 -Sadd tudi ba pha trung ttnh ndi ddt tn/c tUp Qi han chd tdi da dien g i l t do vd tinh tidp xuc vdi day pha, mIc d i y d i t didn Ifldi HA d khu vUe n h i cfla, edng trinh kidn true ddu p h i i dung d i y bpe. Vdi lfldi HA dfldng true eung e l p d khu ddng d i n eung p h i i dung diy boc hoic d p treo dd han chd tai nan vd dien. Tuy nhidn, tai nan dien g i l t v i n ludn hidn hflu do 6 l l y dien, d u dao, cic mdi ndi, d c cho cich dien bj h u hdng ... Viy mot trong d c qui t i c an t o i n dien cp b i n I I ludn c i n h g i i c d d khdng tidp xfle vdi ele bd p h i n mang didn mdt eleh vd tinh.
LUdi ba pha 380/220 V chi d n khi nhu d u dCing dien Idn hole cd d c v i t dung didn ba pha. 6 nOi nhu d u didn it v i khdng d n didn ba pha, se hinh thanh lfldi hai pha - ba d i y hay Ifldi mot pha (hinh 1.2). Lfldi hai pha - ba diy gdm mdt d i y q u i n ngudn chia hai nfla, hai d I u I I hai day pha, didm gifla ndi dat v l dfla ra n g o i i t h i n h d i y trung tfnh. Didn I p danh djnh la 2x220 V.
I Dien Jk Doi song
DIEN THl/dNG THCTC Q
Hinh 1.2-Ludi hat pha vd mdt pha Lfldi mot pha gdm d i y q u i n ngudn mdt pha, mdt d I u ndi ra d i y pha, mdt d I u ndi d i t v i d I u ra n g o i i t h i n h d i y trung tinh. Didn i p danh djnh cua lfldi mdt pha la 220 V.
H l u hdt ludi didn sinh hoat deu thudc loai mdt pha, gdm mdt d i y pha (diy Ifla) v i mdt d i y trung tfnh (diy ngudi). Dung but thfl didn dua v i o ludi didn sinh hoat, chlng han, mdt d l l y ^len, d i y n i o but b i o ed didn (ddn tfn hidu sing), dd l i d i y pha, day cdn lai but b i o khdng dien (ddn tin hidu khdng sing), dd l i d i y ngudi. Ve nguydn tic, ta cd thd sd vao day ngudi, nhung khdng ndn t u ^ tidn thuc hidn, trfl khi cd nhu elu sfla ehfla, l i p dat dien. IVIudn tidp xflc vdi day pha, p h i i di g i n g , ung d e h didn hoae dflng trdn ghe cich didn, hoac dung kim cich didn.
D i y quan ngudn HA ludn ndi d i t trung tfnh v l diem ndi dat dan ra ngoii thanh day trung tfnh. Dd l i Ifldi HA dang dflng d nfldc ta. Khi day trung tfnh bj dflt hole khi day khdng dflng qui cich, d i n di xa q u i chidu d i i cho phep, day trung tinh sd mang dien, tflc la ed didn thd so vdi d i t . D4 khIe phuc hidn tfldng dd, tidu chuan ky thuat yeu elu noi dat lap lai day trung tinh sau mdt khoang cich nhat djnh, thfldng l i 200m v i d diem cudi cfla lfldi HA, tflc noi dung didn (hinh 1.3). He dd gpi l i hd ddt - d i t , ndi dat d day q u i n ngudn v i d ndi dflng didn, tidu ehuin ky t h u l t didn qudc te (lEC) kj/ hidu l i he T-T (theo tidng Phip, tere-tere). Vi nfldc ta ap dung he T-T ndn vide ndi dat lap lai d hd dCing didn phdi I I g i i i p h i p b i t budc.
V i t dung didn thfldng cd vd kim loai hole Idi kim loai hoic c i hai. Phin mang didn dupe eleh didn vdi phan vd /
Idi. Khi cich didn bj hdng, didn se truyen ra vd / Idi kim loai.
Khi dd, ndu ngudi vd tinh sd v i o sd bj didn giit. Vi the, he T-T qui djnh t i t c i vd / Idi kim loai khdng mang dien ddu p h i i ndi d i t . Khi eleh didn bj hdng, didn truydn ra vd / Idi kim loai sd g i y sy cd n g i n mach pha - d i t , thiet bi b i o vd se e l t didn, d i m b i o an t o i n eho ngudi dung didn.
Cic thidt bj dflng didn ed vd / Idi kim loai theo tieu ehuIn didn l i loai cd d i y ndi dat vd / Idi kim lo?i. Phfeh l l y didn l i lo^i ba ehlu, ehlu 1 - d i y pha, c h l u 2 - d i y trung tfnh, ehlu 3 - ndi d i t , tidt didn khie chlu 1 v l 2 . 6 l l y didn eung p h i i I I d ba Id tuong flng! d nflde ta ehfla hinh t h i n h thdi quen niy, ndn ngfldi ta e l t bd ehlu thfl ba cho tidn dung. Nhidu m i y ATfvl b i o chf ndu ngfldi rut tidn bj didn g i i t l i thude Idi niy.
day quin ngudn
- ^ n
H$ d^ng di^n
Hinh 1.3-Ndi dat lap lai
HdHAdungdnUdetallheT-T, c d d i d n a p p h a - p h a 380 V va pha - dat 220 V, trung tinh d i y quan ngudn ndi d i t true tidp. Mach didn sinh hoat thdng thudng ed mdt d i y pha v i mdt day trung tfnh. Khdng dupe tiep xflc vdi day pha ndu khdng ed bidn phap an t o i n . Vide ndi d i t lap lai d hp dflng didn cung nhfl ndi dat vd / Idi kim loai khdng mang didn cfla vat dung dien I I tidu ehuIn b i t budc de b i o d i m an toan dflng didn.
pa Jk D&i swigl 31